Remove lodash from core (#2827)

* Remove `lodash-es` dependency

* Replace `escapeRegExp` with home-made util

* Replace `throttle` with `throttle-debounce` library

* Use native browser methods for `deepFlatten`

We need a polyfill for iOS 11 and below. I think using a native method with this polyfill is better than having our own function instead, even if the bundle size is ~150B more.

* Save a few bytes in `escapeRegExp`

* Fix typo in comment

* Undo import re-organisation

* Use spread instead of slice

* Use smaller Array.flat polyfill from MDN

* Export new utils in `compat.js`

js/src/common/Application.js

@@ -20,7 +20,6 @@ import Discussion from './models/Discussion';
 import Post from './models/Post';
 import Group from './models/Group';
 import Notification from './models/Notification';
-import { flattenDeep } from 'lodash-es';
 import PageState from './states/PageState';
 import ModalManagerState from './states/ModalManagerState';
 import AlertManagerState from './states/AlertManagerState';
@@ -184,7 +183,7 @@ export default class Application {
     Object.keys(extensions).forEach((name) => {
       const extension = extensions[name];
 
-      const extenders = flattenDeep(extension.extend);
+      const extenders = extension.extend.flat(Infinity);
 
       for (const extender of extenders) {
         extender.extend(this, { name, exports: extension });

js/src/common/compat.js

@@ -12,7 +12,9 @@ import Drawer from './utils/Drawer';
 import anchorScroll from './utils/anchorScroll';
 import RequestError from './utils/RequestError';
 import abbreviateNumber from './utils/abbreviateNumber';
+import escapeRegExp from './utils/escapeRegExp';
 import * as string from './utils/string';
+import * as ThrottleDebounce from './utils/throttleDebounce';
 import Stream from './utils/Stream';
 import SubtreeRetainer from './utils/SubtreeRetainer';
 import setRouteWithForcedRefresh from './utils/setRouteWithForcedRefresh';
@@ -91,6 +93,7 @@ export default {
   'utils/abbreviateNumber': abbreviateNumber,
   'utils/string': string,
   'utils/SubtreeRetainer': SubtreeRetainer,
+  'utils/escapeRegExp': escapeRegExp,
   'utils/extract': extract,
   'utils/ScrollListener': ScrollListener,
   'utils/stringToColor': stringToColor,
@@ -104,6 +107,7 @@ export default {
   'utils/formatNumber': formatNumber,
   'utils/mapRoutes': mapRoutes,
   'utils/withAttr': withAttr,
+  'utils/throttleDebounce': ThrottleDebounce,
   'models/Notification': Notification,
   'models/User': User,
   'models/Post': Post,

js/src/common/index.js

@@ -23,3 +23,5 @@ patchMithril(window);
 import * as Extend from './extend/index';
 
 export { Extend };
+
+import './utils/arrayFlatPolyfill';

js/src/common/utils/arrayFlatPolyfill.ts

@@ -0,0 +1,14 @@
+// Based off of the polyfill on MDN
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat#reduce_concat_isarray_recursivity
+//
+// Needed to provide support for Safari on iOS < 12
+
+if (!Array.prototype['flat']) {
+  Array.prototype['flat'] = function flat(this: any[], depth: number = 1): any[] {
+    return depth > 0
+      ? Array.prototype.reduce.call(this, (acc, val): any[] => acc.concat(Array.isArray(val) ? flat.call(val, depth - 1) : val), [])
+      : // If no depth is provided, or depth is 0, just return a copy of
+        // the array. Spread is supported in all major browsers (iOS 8+)
+        [...this];
+  };
+}

js/src/common/utils/escapeRegExp.ts

@@ -0,0 +1,10 @@
+const specialChars = /[.*+?^${}()|[\]\\]/g;
+
+/**
+ * Escapes the `RegExp` special characters in `input`.
+ *
+ * @see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions#escaping
+ */
+export default function escapeRegExp(input: string): string {
+  return input.replace(specialChars, '\\$&');
+}

js/src/common/utils/throttleDebounce.ts

@@ -0,0 +1,3 @@
+// Re-exports `throttle-debounce` to be used in `compat.js`.
+
+export { throttle, debounce } from 'throttle-debounce';